1. Field of the Invention
The present invention is directed to an output or input coupler for multi-mode optical fibers such as light conducting glass fibers.
2. Prior Art
In optical transmission systems, it is often necessary to draw or decouple part of the optical energy or power from a light conducting fiber at a specific point or to additionally input couple optical power or energy into the optical fiber system. The output coupling of a part of the optical part of the system enables supplying an optical unit with a signal or to measure a signal level in the optical system. The input coupling enables an optical unit to feed an optical signal into the transmission lines of the optical system.
Output and input couplers for groups of glass fibers or glass fiber bundles are already known. Examples of these couplers are described in the following two publications: F. L. Thiel, "Topical Meeting On Optical Fiber Transmission", Jan. 7-9, 1975, Williamsburg, Va., U.S.A., Paper WE 1--1, and A. F. Milton, A. B. Lee, "Topical Meeting On Optical Fiber Transmission", Jan. 7-9, 1975, Williamsburg, Va., U.S.A., Paper WE 2-1.
Another known type of glass fiber branch arrangement is a branching fiber core, which is arranged within a common fiber cladding. This known branching arrangement could also be used as an output and input coupler. This known branch arrangement is produced by providing a profile having a branch core, and then drawing the profile to form the appropriate branched glass fibers. However, the production process to produce this type of branch glass fiber is relatively expensive.